The human immunodeficiency virus (HIV) attacks the body's immune system. A healthy immune system provides a natural defence against disease and infection. If the immune system is damaged by HIV, it increases the risk of developing a serious infection or disease, such as cancer.

HIV infects particular cells, called CD4 cells, that are found in the blood. CD4 cells are responsible for fighting infection. After they become infected, the CD4 cells are destroyed by HIV. Although the body will attempt to produce more CD4 cells, their numbers will eventually decline and the immune system will stop working.

How is HIV spread?

HIV is spread through the exchange of bodily fluids. This most commonly happens during unprotected sexual contact, such as vaginal, oral and anal sex. People who inject illegal drugs and share needles are also at risk of catching HIV. The condition can also be spread from a mother to her unborn child.

There is no cure for HIV and no vaccine to stop you becoming infected. However, since the 1990s, treatments have been developed that enable most people with HIV to stay well and live relatively normal lives.

What is a retrovirus?

HIV is a special type of virus known as a retrovirus. The retrovirus reproduces inside the cell and releases copies of itself into the blood. It can be challenging to treat as the virus can rapidly mutate (alter) into new strains of virus.

What is AIDS?

Acquired immune deficiency syndrome (AIDS) is a term that is used to describe the late stage of HIV. This is when the immune system has stopped working and the person develops a life-threatening condition, such as pneumonia (infection of the lungs).

The term AIDS was first used by doctors when the exact nature of HIV was not fully understood. However, the term is no longer widely used because it is too general to describe the many different conditions that can affect somebody with HIV. Specialists now prefer to use the terms advanced or late-stage HIV infection.

Useful Links

If you have suffered an injury (needle stick or other sharps injury, sexual exposure, human bites, exposure of broken skin or of mucous membranes) where there is a risk of transmission of blood borne viruses and other infections, further information on how to manage your situation is at:

How common is HIV?

At the end of 2010, a cumulative 6,000 people were notified with HIV in Ireland. There were 331 new diagnoses reported in 2010. Sex between men (MSM) is now the predominant mode of transmission in Ireland.There were 10 deaths among AIDS cases.

The number of people living with HIV is rising each year. This is because more cases are being diagnosed and people are living longer due to more effective medication.

If you are diagnosed with HIV, you will be referred to an HIV clinic. You will also be offered counselling.

As part of your treatment, you will undergo regular blood tests. The tests are used to measure two things:

  • your CD4 count, which is the number of CD4 cells in your blood
  • your viral load, which is the amount of HIV in your blood

These tests allow the staff at the HIV clinic to see how far the disease has progressed and to judge the likelihood that you will develop an HIV-related infection.

As a general rule:

  • A CD4 count of 500 or above means that there is no risk of HIV-related infection.
  • A CD4 count of less than 200 means that there is high risk of serious HIV-related infection.

The viral load will be regularly measured to show whether the medicines being used to treat HIV are working effectively. The aim of treatment is to reduce the levels of virus in the blood (viral load) to undetectable levels. If you have a detectable viral load while taking treatment, you may need a new combination of medicines.

Both CD4 count and viral load will naturally change with time, so one high or low reading does not automatically mean that your condition has got worse. The general trend of your CD4 count and viral load over time is more important in tracking the progression of the condition.

Combination therapy

There is no cure or vaccine for HIV. However, combination therapy, also called highly active antiretroviral therapy (HAART), slows the progression of the condition and can prolong life. A combination of medicines is used because HIV can quickly adapt and become resistant to one single medicine. HIV medicines are known as antiretrovirals (ARVs).

It is normally recommended that you begin treatment with ARVs if your CD4 count drops below 350.

For a small number of people, treatment may start before the CD4 count drops below 350. This may be recommended by your doctor if:

  • You have an AIDS diagnosis (for example, Kaposi's sarcoma) or any other HIV-related illness.
  • You have hepatitis B infection and it needs to be treated.
  • You have a hepatitis C infection.
  • You have a high risk of heart attack or stroke (cardiovascular events).
  • You are pregnant and need to prevent your unborn child from becoming infected with HIV.

If treatment is not started immediately after diagnosis, your condition will be monitored and regular CD4 counts will be taken.


Many different types of ARV medicine can be used as part of your therapy. A combination of medicines that suits one person may not be suitable for another, so the medicine you take will be individual to you. There are five main types of ARV:

  • nucleoside reverse transcriptase inhibitors (NRTIs) or nucleotide reverse transcriptase inhibitors (NtRTIs)
  • non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • protease inhibitors (PIs)
  • fusion and entry inhibitors
  • integrase inhibitors (INIs)

These medicines work in different ways, but they all stop the virus reproducing inside your cells, slowing down its spread and protecting your immune system.

Most people with HIV are initially recommended to take two types of NRTI/NtRTI medication, plus another type of medicine. The two NRTI/NtRTIs are often combined in a single tablet.

The goal of treatment is to find the best combination of medicines, which reduces the viral load to undetectable levels while minimising any side effects.

Side effects

In some people, the medicines that are used to treat HIV will cause side effects. However, often the side effects improve after a few weeks as your body gets used to the medicines. Common side effects of HIV medication include:

  • nausea
  • tiredness
  • diarrhoea
  • skin rashes 
  • mood changes
  • gaining fat on one part of your body while losing it on another (lipodystrophy)

If the side effects from HIV treatment adversely affect your quality of life, tell the staff at your HIV clinic. It may be possible to change your medicines or other medicines may be available to relieve any side effects.


The medicines used to treat HIV are only effective when taken exactly as prescribed. Missing even a few doses will increase the risk of your treatment not working.

Sticking to your treatment plan is known as adherence. To adhere to treatment, you need to:

  • take the medicine at the recommended time
  • take the recommended dose
  • follow all instructions regarding diet, for example some medicines should only be taken on an empty stomach, while others need to be taken with food

You will need to develop a daily routine to fit your treatment plan around your lifestyle. The staff at your HIV clinic can give you advice and support.

Many of the medicines used to treat HIV can react in unpredictable ways if you take other types of medicines. These include herbal remedies such as St John's Wort, recreational drugs such as cocaine, and over-the-counter medicines.

Always check with clinic staff or your GP before taking any other medicines.

Post exposure prophylaxis (PEP)

It is sometimes possible to halt the development of HIV in the first 72 hours after exposure. This is known as post exposure prophylaxis (PEP). PEP involves taking anti-HIV medicines for four weeks.

PEP is often used when a person knows they have been exposed to HIV. This could be because they had sex with someone who they knew had HIV and the condom broke, or they were accidentally stabbed with an HIV-infected needle.

PEP is not guaranteed to work and the medicines that are used cause some unpleasant side effects, such as nausea, vomiting, diarrhoea and headaches.

If you are concerned that you have been exposed to HIV, immediately contact your local accident and emergency department or GUM (genitourinary) or sexual health clinic.


Useful Links

If you have suffered an injury (needle stick or other sharps injury, sexual exposure, human bites, exposure of broken skin or of mucous membranes) where there is a risk of transmission of blood borne viruses and other infections, further information on how to manage your situation is at:

What can I do if I think I have had unsafe sex with someone who has HIV?

You may benefit from a four-week course of anti-HIV medication, known as post exposure prophylaxis (PEP). For treatment to be effective, it needs to be started within 72 hours (three days) of exposure. However, the sooner it is started, the more effective it is. PEP is usually recommended if you have had unprotected vaginal or anal sex with someone who has HIV or if you have received anal sex from someone with a high chance of having HIV. Although there is no guarantee that you will not develop HIV, it may help protect you.

PEP may also be considered if you gave oral sex (fellatio) to someone who has HIV or is at a high risk of having HIV and they ejaculated (came) in your mouth, or if you have had unprotected vaginal or anal sex with someone with a high risk of having HIV. Healthcare workers who have been put at risk, such as through a ‘needlestick’ injury, may also be advised to have PEP.

You can get PEP at a STI clinic or an A&E department, where the doctor or nurse will ask you several questions to try to ascertain whether you could benefit from treatment.

What happens if I am not treated?

Without treatment, HIV will cause progressive damage to your immune system. It may eventually become so overwhelmed that you develop AIDS, which can be fatal. Research suggests that beginning treatment early in the course of infection may help reduce damage to the immune system. Your doctor can advise you on the best time to begin treatment.

How people cope with being diagnosed with HIV, as well as with treatment, varies from person to person.

Self care

Self care is an integral part of daily life. It means that you take responsibility for your own health and wellbeing, with support from the people involved in your care. Self care includes the things you do each day to stay fit, maintain good physical and mental health, prevent illness or accidents, and effectively deal with minor ailments and long-term conditions. People living with long-term conditions can benefit enormously if they receive support for self care. They can live longer, have less pain, anxiety, depression and fatigue, have a better quality of life, and be more active and independent.

Regular reviews

Because HIV is a long-term condition, you will be in regular contact with your healthcare team. A good relationship with the team means that you can easily discuss your symptoms or concerns. The more the team knows, the more they can help you.

Keeping well

Everyone with a long-term condition such as HIV is encouraged to get a flu jab each autumn to protect against flu (influenza). It is also recommended that they get an anti-pneumoccocal vaccination every five years. This is an injection that protects against a serious chest infection called pneumococcal pneumonia.

Healthy eating and exercise

Regular exercise and a healthy diet are recommended for everyone, not just people with HIV. They can help prevent many conditions, including heart disease and many forms of cancer. Try to eat a balanced diet, containing all the food groups, to give your body the nutrition it needs. Exercising regularly can help relieve stress and reduce fatigue.

Stopping smoking

Giving up smoking can improve your overall health. Visit

Preventing infection

If you have HIV, you should take extra precautions to prevent exposure to infection. Be careful around animals as they can be a source of parasitic infection. Avoid coming into contact with cat litter or animal faeces. Wear latex gloves if you need to clean your pet or dispose of their droppings. Wash your hands regularly, particularly after going to the toilet, before and after preparing food, and after spending time in crowded places.

Psychological impact of HIV hide

Being diagnosed with HIV can be very distressing and feelings of anxiety or depression are common. Your HIV clinic can provide you with counselling so that you can fully discuss your condition and your concerns.

You may find it helpful to talk to a trained counsellor or psychologist, or to someone at a specialist helpline. Your HIV clinic will have information on these.

Some people find it helpful to talk to other people who have HIV, either at a local support group or in an internet chatroom


Useful Links

If you have suffered an injury (needle stick or other sharps injury, sexual exposure, human bites, exposure of broken skin or of mucous membranes) where there is a risk of transmission of blood borne viruses and other infections, further information on how to manage your situation is at:

Pregnancy show

If you have HIV and become pregnant, contact your HIV clinic. This is important because:

  • Some anti-HIV medicines can harm babies, so your treatment plan will need to be reviewed.
  • Additional medicines may be needed to prevent your baby getting HIV.

Without treatment, there is a one in four chance that your baby will develop HIV. With treatment, the risk is less than one in a hundred.

Advances in treatment mean that a normal delivery will not usually increase the risk of transmission from mother to baby for women who have an undetectable viral count and whose HIV is well managed. For some women, a caesarean section may still be recommended.

Discuss the risks and benefits of each delivery method with the staff at your HIV clinic. The final decision about how your baby is delivered is yours, and unless any unforeseen complications make a caesarean section necessary, staff will respect that decision.

If you have HIV, do not breastfeed your baby because the virus can be transmitted through breast milk.

If you or your partner has HIV, fertility treatments may be available that will allow you to conceive a child without putting either of you at risk of infection.

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.

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